A. Tetrachloroethylene, also known as perchloroethylene, or perc, is the predominant chemical solvent used in dry cleaning. Perc is also used in the cleaning of metal machinery and to manufacture some consumer products and other chemicals. It is a clear, colorless liquid that has a sharp, sweet odor and evaporates quickly. It is an effective cleaning solvent and is used by most professional dry cleaners because it removes stains and dirt from all common types of fabrics. Perc is also a toxic chemical with both human health and environmental concerns. To minimize these concerns, EPA is working with the dry cleaning industry to reduce emissions and over time phase out uses of perc in some settings. However, EPA does not believe that having your clothes dry cleaned with perc will result in an increased risk for adverse health effects for you or your family.

Q. How does dry cleaning work?

A. Despite its name, dry cleaning is not totally dry. It involves the use of liquid chemicals called solvents that remove most stains from a variety of fabrics. Most dry cleaners use perc as their primary solvent. Because the clothes are cleaned in a liquid solution that is mostly perc or some other solvent, with very little water if any, the term "dry cleaning" is used to describe the process. There are some differences in the way dry cleaners process clothes, but here is how it typically works:

Dry cleaners usually treat spots by hand before placing garments in large machines.

Liquid solvents, detergents, and sometimes a small amount of water, are added to the machines. The machines then agitate clothes in a manner similar to your own washing machine to remove dirt, oil, and stains.

Once clean, the clothes are either dried in the same machine or transferred manually to a separate dryer, then pressed and shaped.

Used solvent is distilled so it can be purified. Distillation separates the solvent from waste residues such as detergents, dye, dirt, oil, so the solvent can be reused. In addition to distillation, most machines also use filters to clean used solvent.

After the purification process, filters which contain the solvent in very small amounts, and certain solvent residues, such as perc, must be managed and disposed of as hazardous waste. Dry cleaners can send them to special facilities for recycling or incineration.

Q. What are the non-cancer human health concerns associated with perc?

A. At certain levels over a sustained period, exposure to perc can cause adverse non-cancer effects on the human nervous system. Long-term exposure to perc can also pose a potential human health hazard to reproduction and development, and to the kidney, liver, immune and hematologic systems. The risk of any non-cancer health effects from perc exposure depends on the amount of perc a person is exposed to and how long the exposure lasts. People exposed to high levels of perc, even for brief periods, may experience symptoms such as dizziness, fatigue, headaches, confusion, nausea, and skin, lung, eye and mucous membrane irritation.

To further understand the human health effects associated with perc, EPA conducted a comprehensive, in-depth assessment of perc through the Integrated Risk Information System (IRIS) Program. This comprehensive health effects assessment underwent a rigorous peer review process, and all major comments were addressed.

Q. Can perc cause cancer?

A. While EPA has determined that perc is a “likely human carcinogen,” EPA does not believe that wearing clothes cleaned with perc pose a risk of concern. The cancer-causing potential of perc has been extensively investigated. In laboratory studies, perc has been shown to cause cancer in rats and mice when they ingest or inhale it. There is also suggestive evidence, from several studies of workers in the laundry and dry cleaning industry, that perc exposure is associated with elevated risks of certain types of cancer (including bladder, non-Hodgkin lymphoma, and multiple myeloma-- a cancer of the blood). As with all health effects, the potential for an increased risk of cancer depends on several factors including how much perc exposure there is, how often the exposure occurs, and how long it lasts.

Q. How is perc released into the environment?

A. Perc can get into the air, water and ground during the cleaning, purification, and waste disposal phases of dry cleaning.

Outdoor Air
While not a cause for public concern, perc can escape into the outdoor air through open windows, vents, and air-conditioning systems at facilities using perc. Once outdoors, perc can remain in the atmosphere for several weeks. After a few weeks, perc breaks down into other chemicals, some of which are toxic, and some of which are suspected to deplete the ozone layer. Perc itself does not deplete the ozone layer of the atmosphere.

Ground
Perc can enter the ground in liquid form through spills, leaky pipes, leaky tanks, machine leaks, and from improperly handled waste. Significant amounts of perc have been found in waste resulting from dry cleaning, which is considered a hazardous waste by the EPA. Perc is known to be toxic to plants.

Water
Perc can seep through the ground and contaminate surface water, groundwater, and potentially drinking water. A small amount of perc can contaminate a large amount of water and people can be exposed by drinking or using the water. EPA has a limit on the amount of perc that is allowed to be in drinking water. Well water can be tested to be sure it is below the EPA standard. Small amounts of perc in the water can be toxic to aquatic animals and can be stored in their fatty tissues.

A. EPA does not believe that wearing clothes cleaned with perc will result in exposures which pose a risk of concern.

Q. Is it safe to work at a dry cleaning business?

A.The Occupational Safety and Health Administration has set mandatory permissible workplace exposures limits for perc and has established guidance for reducing worker exposure, which includes recommendations for protective equipment and respiratory protection (http://www.osha.gov/dsg/guidance/perc.html).

In addition to worker exposure limits, dry cleaning facilities are required to comply with EPA's perc dry cleaning National Emission Standard for Hazardous Air Pollutants (NESHAP). This NESHAP requires operators to control perc emissions at individual dry cleaners and has reduced the amount of perc released from dry cleaning shops across the country.

However, there may be an increased potential risk for some dry cleaning workers because people who work in dry cleaning shops are expected to have the highest exposures to perc. This is because they spend a lot of time inside the shops where the perc air levels are usually higher than levels found outside the shops. The use of newer dry cleaning machines (dry-to-dry, closed looped) greatly reduce the amount of perc released into the air inside the shop as well as outdoors, resulting in cost savings since more perc is recovered for reuse, as well as safer working conditions and a cleaner environment.

Q. What about people who live or work in the same building as a dry cleaning business?

A. People who live or work in the same building as a dry cleaner can have greater potential for exposures to perc. High perc levels in residences would be of special concern for occupants who are at home a lot and might be exposed to perc for extended periods of time, such as the elderly, young children, or pregnant women. To address this issue, EPA finalized a rule under the Clean Air Act in 2006 that requires operators to control perc emissions at individual dry cleaners. The rule includes a phase-out of perc use at dry cleaners located in residential buildings, along with requirements that already have reduced perc emissions at other dry cleaners.

Q. What is the U.S. EPA’s IRIS Program and what is the final health assessment for perc?

A. The U.S. EPA's Integrated Risk Information System (IRIS) Program evaluates the human health effects that may result from exposure to environmental contaminants. Through the IRIS Program, EPA provides science-based human health assessments to support federal, state, local and other policy making activities. The IRIS Program has an on-line database that contains information for more than 550 chemical substances containing information on human health effects that may result from exposure to various substances in the environment.

EPA has posted the final health assessment for tetrachloroethylene – also known as perchloroethylene, or perc – to EPA’s Integrated Risk Information System (IRIS) database. The final assessment characterizes perc as a “likely human carcinogen.” The assessment provides estimates for both cancer and non cancer effects associated exposure to perc over a lifetime. The assessment will allow for a better understanding of the risks posed to communities from exposure to perc and provide federal, state, local and other policy makers with the latest scientific information to make decisions about cleanup and other actions to protect people's health.

Q. What has EPA done to address air emissions of PERC from dry cleaners and other sites?

A. In 2006, EPA updated its air toxics rule for dry cleaners that requires operators to control perc emissions at individual dry cleaners. The rule includes a phase-out of perc use at dry cleaners located in residential buildings by December 21, 2020, along with requirements that already have reduced perc emissions at other dry cleaners.

In addition, EPA’s 2007 air toxics standards for the halogenated solvent cleaning industry set limits for a group of toxics that include perchloroethylene and trichloroethylene, both of which are referred to as perc.

Q. How will the final IRIS assessment of perc impact the National Emission Standard for Hazardous Air Pollutants (NESHAP)?

A. The NESHAP was issued in 2006 and is in effect. The final IRIS assessment will be considered in future reviews of the standard.

Q. How will the final IRIS assessment of perc impact Superfund clean-up sites?

A. The Office of Solid Waste and Emergency Response (OSWER) will continue to use the Maximum Contaminant Level (MCL) of 5 ppb for perc, established by the EPA Office of Water, as the remediation goal for ground water that may be used as a drinking water supply. At Superfund sites where a state, such as California, has a more stringent standard for perc, that standard will be considered as the cleanup goal.

The new IRIS toxicity values will be used to derive cleanup levels for indoor air contaminated by vapor intrusion. Previously, the Superfund program derived cleanup levels for indoor air based on the California EPA toxicity values. The new IRIS values for perc will be used by the Superfund program to derive cleanup levels for any new sites with indoor air contaminated from vapor intrusion. Because the cleanup levels based on the new IRIS values will be less stringent than the ones based on the California EPA values, no additional cleanup will need to be done at any previously cleaned Superfund sites.

Q. Will EPA’s Office of Water revise the federal Maximum Contaminant Level (MCL) for perc as a result of this assessment?

A. EPA decided to revise the federal Maximum Contaminant Level for perc in 2010 and intends to address the perc MCL as part of a category of carcinogenic volatile organic compounds (VOCs). The agency expects to initiate regulatory efforts to begin addressing carcinogenic VOCs by the end of March 2011. Typically, it takes about 2 to 2.5 years to develop a proposed rule and about 2 years to promulgate a final rule. The final IRIS assessment for perc will be considered in EPA’s review of the best available science and the agency’s responsibilities under the law.

Q. Why are EPA’s toxicity values so different from those of other organizations?

A. There are multiple reasons why it is difficult or not feasible to directly compare EPA IRIS toxicity values to other agencies’ or organizations’ toxicity values, including:

Date of the assessment: A new assessment may cite and use scientific studies that were not available when an assessment from an earlier date was written.

Different Methods: Other organizations may use different approaches or methods from accepted EPA methods and guidance.